Magnetic Resonance Imaging (MRI) scanning is a method of imaging the human body or other fleshy objects, e.g., animals, either alive or dead. It depends on the object being placed in a large and uniform magnetic field (commonly ranging from 0.2-7.0 Tesla field strength according to the particular machine used).
The image is created by disturbance of molecules of the body by radio-frequency (RF) pulses causing resonance of these molecules. After the RF pulse, the molecules realign with the magnetic field and in so doing emit a weak RF signal of their own. This signal is detected and analyzed by a computer and a signal map created of the interrogated body part such that a grayscale image is displayed.
The appearance is usually that of "slices" through the body revealing the inner organs. It is useful in medical practice to place needles in these inner organs in the presence of disease both to extract tissue and fluid samples for analysis (biopsy) or to pass fluids or instruments down the needles to alter the tissue of interest in a variety of prespecified ways.
The precise position of the needle tip is clearly vital for accurate diagnosis and/or therapy in this context.
To use a needle in an MRI scanner, the needle must fulfill all the requirements for a medicinal needle in terms of strength and body compatibility as well as being compatible with MRI imaging apparatus in that it must be both clearly visible when scanned as well as causing no distortion artefact to the final stage. Any magnetic object will distort the magnetic field and thus the image, making accurate placement difficult.
Such needles as are used currently are made of metal alloys with high non-ferrous metal content and a low relative proportion of iron, but these still cause significant artefact, especially at the needle tip, the most important part.
According to the present invention, the needle is manufactured out of non-metallic materials such as carbon fiber, glass fiber, plastics or ceramics so as to cause no artefact on MRI scanning and allow non-distorted tip visualization.
In one embodiment of the invention, the needle is made of fiber composite materials such as carbon or glass fibers wherein the fibers are arranged either axially, spirally, in circular fashion, or in a combination of these orientations. In another embodiment of the invention, the needle is sterilizable by heat, chemicals, and/or irradiation techniques allowing re-use of the needle.